Acids Throughout History

The Acidic Environment‎ > ‎4. Acid/Base Definitions‎ >

Outline the historical development of ideas about acids including those of:

  • Lavoisier
  • Davy
  • Arrhenius
  • Operational definitions: Definitions based entirely on particular observations.
  • The earliest concepts of acids were operational definitions, based on observations such as:
    • Sourness when tasted.
    • Ability to change the colours of indicators.
  • Conceptual definitions: Definitions that attempt to explain observations.
  • As the field of chemistry developed, concepts of acids began to expand into conceptual definitions.


Acid theory
Evidence / Details

Antoine Lavoisier

Acids were substances that contained oxygen
  • Based on the observation that non-metal oxides produced acidic solutions
  • Later disproved, as many basic substances were found to contain oxygen, and some acidic substances were found not to contain oxygen
1810 Humphry Davy

Acids were substances that contained hydrogen that could be replaced totally or partly by metals Based on the observation that when acids reacted with metals, the metal appeared to replace the hydrogen in the acid, causing hydrogen gas to be evolved
1884 Svante Arrhenius

Acids were substances that ionised in solution to produce hydrogen ions
  • Acids were strong if they ionised almost completely, and weak if they ionised only slightly
  • This ignored the role of the solvents